Subcutaneous administration: Difference between revisions

Medications commonly administered via subcutaneous injection or infusion include [[insulin]], [[Attenuated vaccine|live vaccines]], [[monoclonal antibodies]], and [[heparin]]. These medications cannot be administered orally as the molecules are too large to be absorbed in the intestines.<ref name="Adv2019">{{cite journal | vauthors = Usach I, Martinez R, Festini T, Peris JE | title = Subcutaneous Injection of Drugs: Literature Review of Factors Influencing Pain Sensation at the Injection Site | journal = Advances in Therapy | volume = 36 | issue = 11 | pages = 2986–2996 | date = November 2019 | pmid = 31587143 | pmc = 6822791 | doi = 10.1007/s12325-019-01101-6 | name-list-style = vanc }}</ref> Subcutaneous injections can also be used when the increased bioavailability and more rapid effects over oral administration are preferred. They are also the easiest form of [[parenteral administration]] of medication to perform by lay people, and are associated with less adverse effects such as pain or infection than other forms of injection.<ref name="Adv2019" />

Perhaps the most common medication administered subcutaneously is insulin. While attempts have been made since the 1920s to administer insulin orally, the large size of the molecule has made it difficult to create a formulation with absorption and predictability that comes close to subcutaneous injections of insulin.<ref name="insulin2018">{{cite journal | vauthors = Gedawy A, Martinez J, Al-Salami H, Dass CR | title = Oral insulin delivery: existing barriers and current counter-strategies | journal = The Journal of Pharmacy and Pharmacology | volume = 70 | issue = 2 | pages = 197–213 | date = February 2018 | pmid = 29193053 | doi = 10.1111/jphp.12852 | name-list-style = vanc | s2cid = 12848146 | doi-access = free }}</ref> People with [[type 1 diabetes]] almost all require insulin as part of their treatment regimens, and a smaller proportion of people with [[type 2 diabetes]] do as well -— with tens of millions of prescriptions per year in the United States alone.<ref>{{cite web |title=Insulin Human - Drug Usage Statistics | work = ClinCalc DrugStats Database |url=https://clincalc.com/DrugStats/Drugs/InsulinHuman }}</ref>

Subcutaneous injection may also be used by people to (self-) administer [[Recreational drug use|recreational drugs]]. This can be referred to as [[skin popping]].<ref name="neph2016">{{cite journal | vauthors = Lejmi H, Jen KY, Olson JL, James SH, Sam R | title = Characteristics of AA amyloidosis patients in San Francisco | journal = Nephrology | volume = 21 | issue = 4 | pages = 308–313 | date = April 2016 | pmid = 26370715 | doi = 10.1111/nep.12616 | name-list-style = vanc | s2cid = 31760853 | url = https://escholarship.org/uc/item/3h34t4b7 }}</ref> In some cases, the administration of illicit drugs in this way is associated with unsafe practices leading to infections and other adverse effects. In rare cases, this results in serious side effects such as [[AA amyloidosis]].<ref name="neph2016" /> Recreational drugs reported to be administered subcutaneously have included [[cocaine]],<ref>{{cite journal | vauthors = Khan F, Mukhtar S, Anjum F, Tripathi B, Sriprasad S, Dickinson IK, Madaan S | title = Fournier's gangrene associated with intradermal injection of cocaine | journal = The Journal of Sexual Medicine | volume = 10 | issue = 4 | pages = 1184–1186 | date = April 2013 | pmid = 23347293 | doi = 10.1111/jsm.12055 | name-list-style = vanc }}</ref> [[mephedrone]],<ref>{{cite journal | vauthors = Meng H, Cao J, Kang J, Ying X, Ji J, Reynolds W, Rampe D | title = Mephedrone, a new designer drug of abuse, produces acute hemodynamic effects in the rat | journal = Toxicology Letters | volume = 208 | issue = 1 | pages = 62–68 | date = January 2012 | pmid = 22037396 | doi = 10.1016/j.toxlet.2011.10.010 | name-list-style = vanc }}</ref> and [[amphetamine]] derivatives such as [[para-Methoxy-N-methylamphetamine|PMMA]].<ref>{{cite journal | vauthors = Steele TD, Katz JL, Ricaurte GA | title = Evaluation of the neurotoxicity of N-methyl-1-(4-methoxyphenyl)-2-aminopropane (para-methoxymethamphetamine, PMMA) | journal = Brain Research | volume = 589 | issue = 2 | pages = 349–352 | date = September 1992 | pmid = 1382813 | doi = 10.1016/0006-8993(92)91298-s | s2cid = 232653 | doi-access = free }}</ref>

With normal doses of medicine (less than 2 mL in volume), complications or adverse effects are very rare. The most common adverse reactions after subcutaneous injections are administered are termed "[[injection site reactionsreaction]]s". This term encompasses any combination of redness, swelling, itching, bruising, or other irritation that does not spread beyond the immediate vicinity of the injection.<ref name="Derm2019">{{cite journal | vauthors = Thomaidou E, Ramot Y | title = Injection site reactions with the use of biological agents | journal = Dermatologic Therapy | volume = 32 | issue = 2 | pages = e12817 | date = March 2019 | pmid = 30637967 | doi = 10.1111/dth.12817 | s2cid = 58544258 | doi-access = free }}</ref> Injection site reactions may be minimized if repeated injections are necessary by moving the injection site at least one inch from previous injections, or using a different injection location altogether.<ref name="Derm2019" /> There may also be specific complications associated with the specific medication being administered.

Many medications have the potential to cause local lesions or swelling due to the irritating effect the medications have on the skin and subcutaneous tissues. This includes medications such as [[apomorphine]]<ref>{{cite journal | vauthors = Müller T | title = An evaluation of subcutaneous apomorphine for the treatment of Parkinson's disease | journal = Expert Opinion on Pharmacotherapy | volume = 21 | issue = 14 | pages = 1659–1665 | date = October 2020 | pmid = 32640853 | doi = 10.1080/14656566.2020.1787379 | name-list-style = vanc | s2cid = 220435665 }}</ref> and [[hyaluronic acid]] injected as a filler, which may cause the area to appear bruised. Hyaluronic acid "bruising" may be treated using injections of [[hyaluronidase]] enzyme around the location.<ref>{{cite journal | vauthors = DeLorenzi C | title = Complications of injectable fillers, part I | journal = Aesthetic Surgery Journal | volume = 33 | issue = 4 | pages = 561–575 | date = May 2013 | pmid = 23636629 | doi = 10.1177/1090820X13484492 | name-list-style = vanc | doi-access = free }}</ref>

The [[Birmingham gauge#Sizes of hypodermic needles|gauge]] of the needle used can range from 25 gauge to 27 gauge, while the length can vary between {{frac|1|2}}-inch to {{frac|5|8}}-inch for injections using a syringe and needle.<ref name=Taylor/>{{rp|722}} For subcutaneous injections delivered using devices such as [[injector pen]]s, the needle used may be as thin as 34 gauge (commonly 30-3230–32 gauge), and as short as 3.5mm5&nbsp;mm (commonly 3.5mm5&nbsp;mm to 5mm5&nbsp;mm).<ref name="MD2019">{{cite journal | vauthors = Leonardi L, Viganò M, Nicolucci A | title = Penetration force and cannula sliding profiles of different pen needles: the PICASSO study | journal = Medical Devices: Evidence and Research | volume = 12 | pages = 311–317 | date = 28 August 2019 | pmid = 31695523 | pmc = 6717876 | doi = 10.2147/MDER.S218983 | doi-access = free }}</ref> Subcutaneous injections can also be delivered via a pump system which uses a cannula inserted under the skin. The specific needle size/length, as well as appropriateness of a device such as a pen or pump, is based on the characteristics of a person's skin layers.<ref name=Taylor />{{rp|722–724}}

Subcutaneous infusion can be used where a slow rate of fluid uptake is required compared to [[intravenous infusion]]. Typically, it is limited to 1 mlmL per minute, although it is possible to increase this by using two sites simultaneously. The chief advantages of subcutaneous infusion over intravenous infusion is that it is cheap and can be administered by non-medical personnel with minimal supervision. It is therefore particularly suitable for home care. The enzyme [[hyaluronidase]] can be added to the fluid to improve absorption during the infusion.<ref>Menahem Sasson, Pesach Shvartzman, [http://www.aafp.org/afp/20011101/1575.html "Hypodermoclysis: an alternative infusion technique"], ''American Family Physician'', vol. 64, no. 9, pp. 1575-1579 (November 1, 2001).</ref>